This invention relates to aquarium filters, and more particularly to an external aquarium filter which is self priming to restart the filter after the filter stops as a result of halting of the impeller pump of the filter unit.
External aquarium filters are used for providing filtration and aeration of the aquarium water in an aquarium tank. The external aquarium filter is typically mounted on a wall of the aquarium tank and includes a pump such as an impeller unit for drawing water from the aquarium tank into the filter. The water passes through filtration material in the filter and is then returned to the aquarium tank in filtered condition. As the water flows back into the aquarium tank it picks up air and provides the necessary aeration of water.
One such external aquarium filter is described in U.S. Pat. No. 4,512,885 entitled Aquarium Filter Assembly and assigned to the Assignee of the present invention. In that patent there is described an external aquarium filter having a removable intake assembly having one end insertable in the aquarium tank. The other end of the intake assembly fits into an intake chamber in the aquarium filter and supports a centrifugal pump means, such as an impeller, which is positioned adjacent the bottom of the intake chamber. The impeller is located on a rotor which depends through an aperture at the bottom of the intake chamber. Coupled to the aperture is an encapsulated electromagnetic stator unit having a well which is hermetically separated from the electromagnetic unit and receives the rotor. The rotor is magnetically coupled to the stator unit and serves to drive the impeller.
In operation, the impeller draws water from the aquarium tank through the intake assembly into the intake chamber. The intake chamber is separated by a partition wall from a filtering chamber in the filter. As the water fills the intake chamber it overflows the partition wall and enters the filtration chamber where it passes through filtration material. The filtration material can typically include a porous envelope filled with filtration material such as carbon, and the like. As the water passes through the filtration material it is filtered and then flows over a spillway back into the aquarium tank.
Occasionally, the filter stops operating because of various unpredictable problems that may accidentally occur. For example, a large piece of debris may enter the intake assembly and get lodged in the impeller unit thereby locking the impeller and preventing its rotation. A power failure may also occur at which time the electromagnetic stator unit will have deenergized thereby stopping rotation of the impeller unit. Other such accidental occurrences may occur. When this happens, the water in the intake chamber begins siphoning out through the intake assembly and back into the aquarium tank. Such siphoning continues until the intake chamber is drained completely.
The reason for the stoppage may go undetected by the aquarium owner. For example, should there be a power failure while the owner is away from the premises, the user may not be aware of the power failure. During this time the filter will drain. When the power is returned, the filter will not begin by itself since the filter must be primed before it can restart. Specifically, water must be placed in the intake chamber sufficient to cover the impeller unit so that the impeller can cause a suction of the aquarium water through the intake assembly. Without priming, the filter unit will not restart. Therefore, even if the power is restarted, the filter unit will not begin pumping.
On the other hand, should the stoppage be as a result of a blockage of dirt, the unit will not start repumping until the blockage is cleared. During this time, however, the electromagnet unit remains energized and generates heat which may damage the aperture in which the stator is connected and the surrounding area of the aquarium filter.
Accordingly, it would be advantageous if the aquarium filter would not overheat should there be a blockage and should also be able to restart itself without requiring attention of the owner should the problem be a power failure.